Two-cycle engine having coaxial compressor and power pistons



March 20, 1951 H c; SPIER 5,49

' TWO-CYCLE E'INGI'NE HAVING COAXIAL COMPRESSOR AND POWER PISTONS Filed Oct. 18, 1946 I m In W INVENTOR.

HANG E. 51 251;

BY QMQK' ATTYS Patented Mar. 20, 1951 'UNlTED STATES PATENT OFFICE TWO-CYCLE ENGINE HAVING COAXIAL COMPRESSOR AND POWER PISTONS Hans G. Spier, Hamilton, Ohio Application October 18, 1946, Serial No. 703,947

. 4 Claims. 1

This invention relates to internal combustion engines and is particularly directed to the aspiration system of two cycle compression ignition engines. The primary object of the invention is to provide a two cycle compression ignition engine in which a power cylinder is scavenged by air from a coaxial compressor cylinder, the piston of which operates in a substantially opposite direction to the piston in the power cylinder for the purpose of balancing vibrational forces arising in the engine.

Another object of the invention is to provide means to control and promote the fiow of scavenging and charging air to the working cylinder of a two cycle compression ignition engine in such a manner that efiective scavenging of the crankcase is obtained without the use of valves containing moving parts.

Another object of the invention is to provide a two cycle compression ignition engine having a separate scavenging air cylinder operating in conjunction with crankcase scavenging air ports in such a manner that lubricating oil vapor carried in the crankcase scavenging air is utilized for aiding the lubrication of the compressor and power cylinder.

Other objects and advantages of the invention will become apparent from the following specification, reference being had to the accompanying drawings in which:

Figure 1 is a somewhat diagrammatic, central vertical sectional view taken in a plane across an engine embodying the present invention; Fig. 2 is a view similar to Fig. 1 showing the parts in another operating position; and Fig. 3 is a central vertical sectional view of the engine taken in a longitudinal plane.

Referring to the drawings, 1 designates an engine base or crankcase in which a crankshaft 2 is journalled. A Single cylinder engine is shown for purposes of illustration, but it will be obvious that multiple cylinder engines may be constructed with no more than conventional variations from the form shown.

A working piston 4 operates in a cylinder 5 extending from the engine base and the upper end of the cylinder is cooled in any suitable manner as by a water jacket 6. The lower end of the cylinder extends as a sleeve or skirt which serves to guide the working piston and also forms an inner wall of an annular scavenging air cylinder I0, the outer wall of which is designated l2.

A scavenging air piston M of annular form operates in cylinder I0 and is connected to crankshaft 2 by spaced connecting rods l6 and I! at each side of a, main connecting rod [8 for the main piston 4. The cranks to which the pistons 4 and [4 are connected are displaced with respect to each other, as shown in Fig. 2, by an amount less than 180, so that while the'pistons operate nearly in phase opposition the scavenging piston reaches its upper dead center position after the working piston has passed its bottom dead center position, as hereinafter described.

The engine shown in the drawings utilizes a crossflow scavenging system, but the invention can be equally well applied to other forms, such as unifiow 0r loop scavenging. In the form shown exhaust ports 20 are provided at one side of the working cylinder While intake ports 22 are disposed on the opposite side in direct communication with scavenging air cylinder [0. The exhaust and intake ports are piston controlled and the timing is substantially convention-a1 with the exhaust ports opening about before bottom center and the intake ports opening about 60 before bottom center.

Air enters the scavenging air cylinders through ports 24 controlled by piston [4, the ports being opened towards the lower end of the piston stroke. The height of piston I4 is made such that at the upper end of its stroke the piston again clears ports 24 so that aircan pass from atmosphere into the crank space of the engine to be compressed as the scavenging piston moves down on its suction stroke. vAir thus compressed is passed to the scavenging cylinder through a plurality of side passages 28 the terminus of which is controlled by the scavenging pistonand opened near the bottom of its stroke so that air under pressure in the crank case is free to flow into the scavenging air space thereby scavenging the crankcase and air-cooling that part of the lubricating oil and lubricating oil vapor which is exposed to the flow of scavenging air through the crank space.

Fuel for the engine is admitted by a conventional nozzle 3!) fed and controlled by a fuel pump 32, injection taking place, as is usual, at or slightly before the working piston 4 reaches top center position.

Inooperation, air is drawn into scavenging air cylinder l0 through ports 24 and ports 28 as the piston l4 opens these ports near the bottom of its stroke. This air is compressed by the piston l4 during its upstroke and discharged into the main cylinder through ports 22 when these ports are opened by the downward travel of main piston 4. It will be apparent that the scavenging air compressing piston l4 must travel toward the top of its stroke at the time the intake ports 22 are first uncovered by main piston 4 so that the sufl'icient air pressure is available for scavenging and charging the main cylinder during the longest available time. Since the intake ports 22 are uncovered 60 before piston 4 reaches the lower limit of its stroke, a considerable lead must be imparted to compressor piston I4.

Since the pistons 4 and 14 move in substantially opposite directions there is a tendency for the engine parts to be balanced dynamically if the proper mass is imparted to the two pistons. Thus a counterweight 15 carried by the common crankshaft can readily complete the dynamic balancing of the unit. The counterweight need not be unduly large since, as above noted, substantial balance is obtained by the opposite movement of the two pistons.

While piston I4 is moving through the upper portion of its stroke, ports 24 are open to the crankcase so that a fresh charge of air is drawn into this space. This air is compressed as piston It moves down and at the same time a small quantity of lubricating oil is entrained. The air and its free oil are passed through ports 28 into the scavenging air cylinder where the oil is deposited on the surfaces of the cylinder to lubricate these walls for the passage of piston i l. The pressure in the crankcase is never so great as to require careful packing, since the two pistons i and 14 move in generally opposite directions, displacement of the larger piston Hi tending to enlarge the crank space somewhat more than piston 4 tends to decrease it. The breathing efficiency of the crankcase can be readily controlled by varying the relative size of ports 24 and 28, and the degree of pressure attained can be regulated by changing the relative area and swept volume of pistons l and [4.

While the invention has been described in connection with a specific form and disposition of the parts, it should be expressly understood that such description pertains only to a preferred form and that numerous modifications and changes may be made without. departing from the. scope of the appended claims.

What I claim is:

1. In a two cycle internal. combustion engine, a power cylinder, a. power piston operating in said cylinder, a compressor cylinder, a compressor piston operating in said compressor cylinder, a closed crank space underlying both of said pistons, ports controlled by said compressor piston to admit air to said crank space and to said compressor cylinder at opposite ends of its stroke, means to conduct air compressed in said crank case into said compressor cylinder, and

means to admit air compressed by said com pressor piston into said working cylinder.

2. A two cycle engine as defined in claim 1 in which said power cylinder and said compressor cylinder are concentric and said pistons operate from a common crankshaft in substantially opposite directions, the mass of said pistons bein such as to effect a substantial dynamic balance of the reciprocating system.

3. A two cycle engine as defined in claim 1 in which said power cylinder and said compressor cylinder are concentric and said pistons operate from a common crankshaft in substantially opposite directions, the mass of said pistons being such as to eiTect a substantial dynamic balance of the reciprocating system, and a counterweight on said common crankshaft to substantially complete the dynamic balance.

4. In a two cycle internal combustion engine, a power cylinder, a piston operating in said cylinder, an annular compressor cylinder surrounding said power cylinder, a compressor piston operat ing in said compressor cylinder, said compressor piston having a larger displacement than said power piston, a closed crank space underlying both of said pistons, ports controlled by said compressor piston to admit air to said crank space when said compressor piston nears one end of its stroke and to said compressor cylinder when said compressor piston nears the opposite end of its stroke, the air in said crank space being compressed as said compressor piston moves to diminish the crank space volume, openings in said compressor cylinder walls controlled by said compressor piston to admit air from said crank space to said compressor cylinder, and piston controlled ports in said power cylinder to admit air from said compressor cylinder, and to exhaust burned gases therefrom.

HANS G. SPIER.

REFERENCES CITED The following references are of record in the 7 file of this patent:

UNITED STATES PATENTS Number Name Date 1,023,957 Peache Apr. 23, 1912 1,042,572 Lee Oct. 29', 1912 1,219,983 Montbarbon et a1. Mar. 20', 1917 1,932,332 Bernard Oct. 24,1933 2,042,722 MacKenzie June 2, 1936 FOREIGN PATENTS Number Country Date 7 588,427 France of 1925 

